Seven members of the Shia minority were shot dead in the Eastern Province district of al-Ahsa on November 3 as they gathered to commemorate Ashura.
Saudi Arabia put down an upsurge by armed groups a decade ago, but fear is building over the possibility of fighters from the ISIL or al-Qaeda affiliate Nusra Front, now operating in Syria or Iraq, radicalizing Saudis to mount a new wave of strikes inside the kingdom.
Last week, the ministry said fighters were trying to attack Saudi Arabia, but that it was not aware of any evidence that the al-Ahsa attack had been coordinated with the ISIL.
On Monday, the official news agency cited an Interior Ministry security spokesman as saying that 77 suspects had been arrested so far, and that they were believed to include the four main perpetrators.
He said the leader of the al-Ahsa attack had received orders from abroad, and that "the target, as well as those to be targeted and the timing were all specified for him, as well as the provision that the (attack) be carried out in al-Ahsa".
The leader had picked three followers, and these had scouted out the target, seized a car, killed its owner, and used it in the attack, Reuters reported.
The spokesman said security forces carried out operations "to arrest everyone affiliated with this terrorist group, whether those who pledged allegiance to the leader of the group, or participants, supporters, financiers, or those who provide cover".
Two Saudis and a Qatari were killed as they resisted arrest, along with two security officers, the ministry said.